Propeller and method of making same



June 18, 1940. w J. BL NH RD 2,205,132

PROPELLER AND METHOD OF MAKING SAIE Filed June 10, 1936 3 Sheets-Sheet 2yw w June 18, 1940. w, J, BLANCHARD 2,205,132

' PROPELLER AND METHOD OF MAKING SAME Filed June 10, 1936 3 Sheets-Sheet5 H125 F VIE/'54? D 76 /NVENTOR Patented June 18, 1940 UNITED STATESPROPELLER AND METHOD OF MAKING SAME Werner J. Blanchard, Dayton, Ohio,assignor'to Engineering Projects, Inc.,-' Dayton, Ohio, a corporation ofOhio Application June 10, 1936, Serlal No. 84,523 Claims- (Cl. 29-1563)This invention relates to propellers and more in particular toimprovements in and novel method of manufacturing aircraft propellers.

. In accordance with the prior art practices, the 5 making of hollowsteel blades is accomplished by making use of either a single sheet ortwo sheets of metal by welding the overlapping or abutting edges alongeither or both of the leading or trailing edges. In such previouspractices '10 the thickness of the metal of the component jointedsections was substantially the same, so that both sections were subjectto comparably high strains and stresses in service operation.

Considerable difliculties have also been experienced in the constructionof hollow steel blades having folded leading and trailing edge portions.In such constructions the folding of the edge portion in manufactureweakened the structure to such an extent that incipient cracks occurredafter short usage.

itself of sustaining or supporting a major portion of the load to whichthe blade may be subject in service operation and constituting thethrust side of the blade, the other section being 9. rolled sheet thatis relatively much thinner than the forged section and serving as thecamher side to complete the blade airfoil and giving to the blade therequired torsional stiffness to avoid objectionable flutter effects. 4The particular weaknesses along the leading and trailing edges of theprior art devices are practically eliminated by providing the forgedsection with forged portions along'the leading and trailing edges ofsufficient thickness so as to be capable in themselves of withstandingthenormally compressive and tension loads of the blade sion and tensionstresses over alarge area to ob- ,tain small unit.values while obtainingthe advantage of having the bond located at a point in the blade wherethe shear stress is a relatively low value. It is a further object of myinvention to provide a method of making a hollow propeller blade inwhich the root and shank portions are 5 formed from a solid metalportion of the forged section and working "the solid portion to providea hollow that extends axially of the blade from the root end to thecavity or cavities in the airfoil portion of the blade. This has the 10advantage that not only is the number of joints, in constructing thehollow blade from two sections, kept at a minimum, but that the joiningof metal portions at the root and shank portions, where the propellerloads are greatest, is avoided. 16

A further object of my invention is to provide a novel bladeconstruction which lends itself to the use of standard machinerypractices thus making it cheap'to manufacture.

A still further object of'my invention is to 20 provide a novel processof manufacture for producing hollow blades that will be consistent andnon-varying during production.

Another object of my invention is to provide a novel method of massdistribution for varying 5 the vibration characteristic without changingthe outward .contour of the blade.

Various other advantages, characteristics and features of my inventionwill become apparent from the following detailed description taken in soconnection with the accompanying drawings.

My invention resides in the method, arrangement, features andcombination of parts of the character hereinafter described and claimed.

In referring to the drawings: 85

Figs. 1 andla are respectively an edge view and an end elevational viewof a metal billet;

Fig. 2 is an edge view showing a forging in the rough shape of apropeller blade section;

' along the lines 4-4 to 9-9 or Fig. 3;

Fig. 10 is an edge view of the blade forging shaped to the final form; v

Fig. 11 is a plan view of Fig. 10; Figs. 12 to 17 inclusive aresectional views alonir the lines lZ-l2 to l'|-l'l of Fig. 11;

Fig. 18 is a sectional view of a forming die;

Fig. 19 is an edge view showing a milling or profilemachine;

Fig, .20 is a section taken along the line 20-20 I of Fig. 19;

Fig. 21 is a plan view of a finished blade torsing; 68

progressively decreasing cross-sectional Non the lines 21-21 to 32-32 ofFig. 26;

Fig. 33 is a fractional enlarged view of the propeller blade; and

Figs. 34 to 36 inclusive are further enlarged section-a1 views taken onthe lines 34-34 to 3636 of Fig. 33. v As illustrated herein, the bladeis constructed from a metal billet that is forged into blade form andfrom a metal blank shaped to conform to one of the faces ofthe finallyshaped forging. The forging A Fig. 21 consists of integral shank andblade portions .that are suitably recessed to reduce the weight withoutchanging the general shape of the blade while maintaining sufficientrigidity in the shank and blade portions such that the shank portion iscapable of sustaining for a useful period the loads to which the blademay be subject and the blade, although less capable of sustaining theloads, will when supplemented by the additional rigidityafforded theblade portion in uniting the relatively thin formed metal section B,Fig. 24, to the forging, be capable of sustaining such loads over asimilar useful period. The rolled metal blank consists of a thincovering conforming to the general outline of the hollowed face of theforging and preferably extends substantially throughout the effectivelength and width of the blade portion and in overlapping relation withthe inner end of the shank portion and the tip end of the blade portion.The two metal sections are united into an integral structure by suitablewelding processes.

In the process of manufacture a round bar or billet of steel A (Fig. 1)formed preferably from an alloy steel of the nickel molybdenum type isheated to a temperature within the critical range and worked into therough shape of a blade, as shown in Figs. 2 and 3'by suitable forgingoperations as rolling, hammer forging,and the like.

The shaping of the billet into rough form as shown in, Figs. 2 and 3 maybe accomplished in a single forging step or several steps. Asillustrated herein, the sectional area of the blade portion'of the metalbillet is reduced fromapproximately the dotted line in Fig. 1 inopposite directions to different extents to provide the rough shapeshank and blade portions, the blade portion reduction providing a bladeportion of from the inner to the outer extremity. thereof whereas thereduction for the shank portion provides the shank portion ofsubstantially uniform cross-sectional area. The sectional area of theshank portion of the metal billet is reduced to such an extent as willprovide a blade shank portion of suitable length and diameter.

The sectionsof the elongated blade portion extending from the point ofmaximum area toward the tip end as shown in Figs. 4 to 9. are preferablysubstantially rectangular in cross-sec iton and those sections extendingthrough the shankportion and to the root end are circular incross-section, each section of the blade'portiom having areas thatapproximate that of the corresponding sections of the further formedblade partion as shown in Figs. 12 to 1'7.

area

' blade length.

To form the blade portion into the shape as shown in Fig. 10, it isagain heated to a temperature at which it is easily workable and pressedinto shape by the action of forging dies-I0, l2, as shown in Fig. 18.The dies are so designed as to give the blade portion the desired pitchand final shape. Several heating and pressing operations may be requiredto bring the blade into its final shape.

The forging dies are preferably designed so that the final shape of theblade portion I4 is formed with two longitudinally extending cavitiesl6, l8 that provide a central longitudinal rib 20, a rib 22 at theleading edge and a rib 24 at the trailing edge. The outer-surfaces orfaces 26,

28, 30 of these ribs respectively define the general outline of theanti-thrust surface of the blade portion and they merge into the shankportion 32 at one end and into a hat surface 3.4

v at the tip portion of the blade at the other end.

angles to the bottom surfaces.

In pressing the blade portion into its final shape, the metal is furtherreduced producing further improvement in the grain structure'and in theflow lines of the metal. v

It will, of course, be understood that while the blade forging isdescribed as being formed into its final shape by die forging, it is notintended to limit the invention to this manner of forging but thatvarious other and well-known forging and rolling operations may beemployed for the purpose of shaping or forming the blade portions.

The lengthening of the original billet into the rough shape bladeproduces flowlines lengthwise in the blade which is desirable and thedie forging thereof displaces the material in such a manner as to retainthe proper direction of flow lines. "Inorder to improve the physicalproperties of the forging, it is subjected to a heat-treatment that issuitable to the particular steel alloy that is used in-making theforging. In the example illustrated therein, the nickel molybdenum alloyand-the process of heat-treating to improve the physical properties andparticularly the elongation, Brinell hardness and tensile strength iswell known in the prior art. After heat treatment the forging isstraightened, if necessary.

In the finishing operations of the forging, the round sections of theshank portion can be machined to an approximate size on a. lathe and the'hollow, '48, shown in Fig. 21, with the hollow boring operations. I

' In accordance with one of the features of my invention, the side andbottom surfaces of' the cavities 16,- I8 and the thrust face 54 of theblade extending substantially throughout the effective length of theblade portion are made up of a series of helical surfaces of varyingpitch angle that converge from points substantially at the maximum cardtoward the tip of the blade so that the rib and intermediate portionstaper both in depth and width substantially throughout the Thisprinciple'of design permits the major machining work on the blade to beaccomplished in a variety of different machines such as, forexample, ahorizontal grinder, a horizontal or vertical milling machine, a planeror a shaper.

In Figs. 19 and 20, I have illustrated a device to generate. thesegeometric surfaces- The generating of these surfaces is accomplished byrotating the blade about its longitudinal axis a:a: in exact relation tothe desired aerodynamic angle distribution or pitch, For this purposethe forging is fixedly seatedupon a suitably formed platen 56 which, inturn, is fixedly supported upon a cradle 58 that is pivotally connectedto a saddle .60 in such a, manner that the'axis of pivotation of thecradle and the longitudinal axis of the blade are practicallycoincident. The

' cradle has attached to the bottom thereof a pair of cams 62, 64 thatengages a cylindrical rotatable follower 66 whose axis of rotation liesin vertical cutting edge of the tool and the work are alwaysin parallelrelation, the machined surface at that point will likewise be parallelto said lines of contact and the machined surfaces substantiallythroughout the length of the blade will be in the -'-blade. will producestraight lines.

and side surfaces or shapes of each of the caviform of a-helical shapeof varying pitch angle corresponding to the generating surface of thecams. These shapes are such that a section taken at right angles to thelongitudinal axisof the The bottom ties l6, 18 are rounded to formfillets. The provision of such fillets will avoid localized highstresses which would otherwise be present. Since the cutting edge of thetool cuts in a horizontal plane and since the bottom surfaces of thecavities l6, I! as well as the thrust face 54 of the bladerespectivelyare designed to converge towards the axis .1:rc of the bladein -the direction of the tip, the axis :cz is therefore displaced asrequired from the horizontal plane byadjusting the saddle 60 through apivot connection 10 at one e'ndand an, adjusting screw I2 at the other.The walls of the cavities are similarly machined but the work isdisposed at right angles tothe position own in Figs. 19 and 20.

The upper faces 26, 28, of the rib portions 20, 22, 24 and also theupper faces 34, at

the opposite ends of the blade portions are ma-' chined in any suitablemannbr as by means of a form milling cutter to provide smooth surfacesfor intimate engagement with the corresponding areas of the cambersection.

. In the process of manufacture a rolledsheet-B I of alloy steel metal,such as nickel molybdenum is shaped preferably while cold into thecamber section B' by a forming die, not s own, to have a curvaturecorresponding to the general outline defined by the faces 25, 2 8, 30,34, 35 and as shown in Figs. 23, 24 and in the cross-sectional views in"Figs; 28 to 32 I have illustrated as one embodinient of my inventiontheuse of a relatively thin sheet of metal of uniform thicknesssubstantially throughout the length thereof. The thicknessof the metalsheet B is such as to provide with the blade portion of the forging anairfoil portion- J having desirable dimensions for goodaerodynamicfefllciency.

The camber ratio at the tip end of the blade is very small and thisratio will vary slightly depending upon the relative size of the bladewith respect to its design length. The thickness of the blade tip at thetrailing edge of the forging being approximately equal to the maximumthickness of its camber section it becomes necessary, order to provide asufllciently large contacting area along the tip edges of said sections,and to avoid a substantial reduction in thickness of the camber section,to form the tip end of the forging with a beveled surface II, as shownin Fig. 33. This beveled surface 14 extends around the tip edge topoints on the leading and trailing edges where the combined metalthickness of the camber and forging sections is equalto that of thecamber of the designed blade at such points, and to shape the tip sothat, at the points where the metal thickness of the camber section isap- --proximately equal to or greater than the edge thickness of theblade tip, the cross sections of the forging will have chords that aresmaller than the chordsof the corresponding cross-sections of the cambersection, as shown in Fig. 36.

The inner end 16 of the camber section shaped to-conform to the designedoutline of the blade at that point and is faired into the shank portionof the forging so that the outer surface joins with the outer surface 35of the shank portion 32 and the inner surface has intimate contact overa relatively large area. It will be seen that all of the contactingareas between the forging and the camber sections are made relativelylarge in order toprovide a bond of high strength value.

It will be understood that the camber sec.- tion may, if desired, beformed from a longitu dinally tapering thin sheet of alloy steel andthat the tip end portion may be of uniform thickness or tapering.

The composite hollow blade as thus fabricated with its relatively heavymain supporting section and relatively thin and lighter camber sectionhas a .weight distribution. different from the distribution of its crosssectional areas providing for the carrying of greater loads in the mainsupporting section than in the camber section. Thus as shown in Figs. 29through 32 and in Figs. 34,.

to 36, the centers of gravity transversely of the blade substantiallythroughout the length thereof are materially ofiset from the centers ofthe total areas of the sections and toward the thrust face of the blade.

The blade is fabricated by assembling the two sections A, B and unitingthe, same through strong bonding provided at their intimate contactingareas. This may be accomplished by various methods of metal bonding,such as fusion welding orby brazing. v

As illustrated the two sections are united together by thewellknowncopper hydrogen furnace brazing method. Copper is.used for aspelter because of the amnity-of molten copper for iron and the easewith which it wets and flows upon a hot steelsurface. This attraction ofiron for copper makes possible the provision of fillets I8 at 'the innerseams of .the joints between the rib portions and :the camber sectionand itis accomplished by placing a sufficient quantity of copperadjacent the seams to flow into the jointsand wtfthe adjoining surfacesat theseams, when .the blade is heated in a hydrogen atmosphere to atemperature above -the melting point of copper. Either copper paste or acopper wire may be used for this purpose.

. sponding points,

making a propeller .blade which comprises work-' ing'a piece of metalinto rough shaped root and blade portions by extending the metallongitudinally of the blade portion to a predetermined progressivelydecreasing cross sectional area and to produce longitudinally extendinglines of flow of the metal, forging the metal transversely of the bladetoward the peripheral edges thereof "while maintaining substantiallysaid predetermined longitudinal distribution of metal and maintainingsaid longitudinal lines of flow of the metal and thereby providing athrust face having leading and trailing edge portions of greaterthickness than said thrust face extending from the shank of the bladeoutwardly to the tip end thereof with said leading and trailing edgeportions projecting inwardly of said thrust face and having slopingsurfaces of substantial area defining therewith a general airfoil shapewith a cavity formed between said edge portions, the totalcross-sectional areas of the formed blade section progressivelydecreasing from the shank of the blade to the outer extremity thereofwithout abrupt change of section, and bonding to said sloping surfacesof said leading and trailing edge portions and to said tip portion tooverlie said portions with a substantial contacting area a plate adaptedto complete the camber side of said blade.

2. In propeller manufacture, the method of forming a part of a hollowpropeller blade which comprises forming a piece of metal into the roughshape of propeller root and blade portions by extending the metallongitudinally of the blade portion and of the root portion to provide asubstantially uniform cross sectional 'area in said root portion and aprogressively decreasing cross sectional area from the inner to theouter end of said blade portion, the extension of said metallongitudinally providing lines of flow of metal in the longitudinaldirection of said blade, and thereafter forging said blade portion tocause flow of the metal transversely thereof with the formation of athrust face having an intermediate and marginal ribs with cavitiestherebetween while maintaining substantially the same longitudinaldistribution of metal, the cross I sectional area of said forged bladebeing generally proportional with the cross sectional areas of saidexpanded rough shaped blade at corresaid marginal ribs having greaterthickness than that of the adjacent thrust face of the blade and withsaid thrust face cor/stituting the main support for the normal loads towhich the blade is subjected, the forging operation providing forforming said thrust face and said ribs in a series of helical surfacesof varying pitch angles that" converge from points at substantially themaximum cord to the tip of the blade.

3. a method in the ma ufactures: a hollow which comprises forming apiece blade propeller the rough shape of a propeller of metal into bladeportion with the blade' portion tapering in graduated -manner inthickness from the shank .to the outer end thereof thereafter forgingthe metal transversely of the blade portion to form marginal ribs and anintermediate upwardly extending rib portion defining longitudinallyextending cavities terminating inwardly of the outer end of said bladeleaving a tip portion .prising an integrated having a cross sectionalarea at the zone where said cavities end correlated with the crosssectional area of the adjacent cavitated portion of the blade tomaintain a predetermined progressively decreasing distribution of metalthroughout said blade beyond the shank thereof without abrupt change inthe .cross sectional area thereof, and thereafter bonding to saidmarginal and intermediate ribs and to said tip portion 'a relativelythin metal plate forming the chamber surface of said blade and adaptedto maintain a predetermined regulated distribution of metal throughoutthe entire blade, said metal plate overlying said marginal andintermediate ribs and being extended outwardly beyond said ribs andcovering said tip portion in overlying bonded relation thereto. a

4. A hollow blade for aircraft propellers comblade formed of a mainsupporting section extending throughout the length of the bladeconstituting the shank and the thrust'face of the blade andhavinglongitudinally extending intermediate and marginal ribs of greaterthickness than said thrust face defining elongated cavities extendingaxially of the blade, said ribs and said cavities terminating inwardlyof the end of the blade leaving a tip portion, the total cross sectionalarea of the ribbed portion of the blade beyond the shank and of said tipportion being graduated in progressively decreasing manner outwardly ofthe blade, said blade also having a camber section relatively thin withreference to said main supporting section completing the airfoil shapewith the main section, said camber section being bonded to-saidintermediate rib and to said marginal ribs over a substantial area andextending substantially to said thrust face at'the leading and trailingedges, and being also joined by a bond that extends to the extreme endof said tip portion to provide a substantial area of contact betweensaidsections with low unit stress.

5. A hollow. blade for aircraft propellers comprising two worked metalsections, onesection forming the thrust face extending throughout thelength of the blade and forming the main shape and provided withcontinuous outstanding ribs along the marginal edges of the side of theblade opposite that forming the thrust face, said ribs havingprogressively decreasing cross-sectional area from the shank to the tipend of the blade delimiting a longitudinal cavity, said blade having adistribution of metal such that the total support for the forces actingon the blade, said sectionhaving a blade portion of general airfoilshank portion and overlying saidribs and said cavity, said other sectionalsoextending beyond said ribs and said cavity .and covering said tipportion in overlying relation thereto with a substantial contacting areadistributed over the blade, said other section being bonded to said ribsand to, said tip portion on the overlying areas thereof to enclose saidcavity and to complete the finished camber surface of said blade.

for aircraft propellers comprising a forged element extending over thewhole length of the blade and constituting the main'"'support of theforces acting on the blade, said element having a 6. A thrust facesection for a hollow blade,

1 shank portion and extending'outwardly therefrom to form the thrustside of the blade and on the anti-thrust side having leading andtrailing edges provided with continuous ribbed portions extendingoutwardly from the shank of the blade and delimiting a longitudinallyextending cavity, said ribs and said cavity tapering out leaving a tipportion at the outer end of the blade,

I said .blade having flow.. lines of the metal extending longitudinallythereof and a mass distributtion of the metal of said blade outwardly ofsaid shank portion such that the total cross-sectional areas of saidblade progressively decrease from. the shank to the outer extremitythereof without abruptchange and providing a blade section in whichthereare'no-sudden variations in the internal stress of each .crosssectionand in'the amount of strain on any two successive cross sections.

7. A hollow blade for aircraft propellers comprising two worked metalsections, one section forming the thrust face extending throughout thelength of the blade and forming the main support for the forces actingonthe blade, said section having a blade portion of general airfoilshape and provided with continuous outstanding intermediate and marginalribs on the side of the blade opposite that forming the thrust face,said ribs having progressively decreasing crosssectional area from theshank to the tip end of the blade delimltin'g a longitudinal cavity,said blade having a distribution of metal such that the totalcross-sectional areas thereof progressively decrease outwardly of theblade to the outer end thereof without abrupt change of section, saidribs and said cavity terminating short of the end of the blade leaving atip portion, and another relatively thin section extending from saidshank portion and overlying said ribs and said cavity, said othersection also extending beyond said ribs and saidcavity and covering saidtip portion in overlying relation thereto 'with a substantial contactingarea distributed over the blade, said other section being bonded to saidribs and to said tip portion on the overlying areas thereof to enclosesaid cavity and to complete the flnishedcamber surface of said blade.

8. A hollow blade for aircraft propellers comprising two worked metalsections, one section forming the thrust face extending throughout thelength of the blade and forming the main support for the forces actingon the blade, said section having a blade portion of general airfoil:shape and provided with continuous outstanding ribs along the marginaledges of the side of the blade opposite that forming the thrust face,said ribs having progressively decreasing cross-sectional. area from theshank to the tip end of the blade delimiting a longitudinal cavity, theshape of said cavity and the ribs defining the same being such thatcross-sections through said-blade portion produce; straight lines at thesurfaces delimiting said cavity and with rounded fillets at the meetinglines of t he bottomand side surfaces of the cavlty, said blade having adistribution of metal such that the total crosssectional areas thereofprogressively decrease outwardlyof the blade to the outer end thereofwithout abrupt change ofsection, said ribs and said cavity terminatingshort of the end of the blade leaving a tip portion, -and anotherrelatively thin section extending from said shank portion and overlyingsaid ribs and said cavity, said other section also extending beyond saidribs and to said tip portion onthe overlying areas thereof to enclosesaid cavity and to complete the finished camber. surface of said blade.

9. A hollow blade foraircraft propellers comprising two workedmetal'sections, one section forming the thrust face extending throughoutthe length of the blade and forming the main support for the forcesacting on the blade, said section having ablade portion of generalairfoil shape and provided with continuous outstanding ribs along theleading and trailing edges on the side of said blade section oppositethat forming the thrust face, the surface of each of said ribs adjacentthe leading and trailing edges being formed respectively inpredetermined manner corresponding substantially to the camberoutline ofthe blade in that area to receive a camber plate in overlying relationthereto over an extended area and in the predetermined desired airfoilcontour, said ribs having progressively decreasing cross-sectional areafrom the shank to the tip end of the blade and delimiting a longitudinalcavity, said blade having a distribution of metal suchthat the totalcross-sectional areas thereof progressively decrease outwardly of theblade to the outer end thereof without abrupt change of section, saidribs and said cavity tapering out adjacent the outer end of the bladeleaving a tip portion, and another relatively thin section extendingfrom said shank portion to the tip of the blade and overlying saidcavity and said tip portion, said other section covering and contactingsaid ribs and said tip portion witha substantial contact-1 ing areadistributed over the blade, said other section being bonded to said ribsand to said tip portion on the overlying areas thereof to enclosesaidcavity and to complete the finished camber surface of the blade.

10. A hollow blade for aircraft propellers comprising two worked metalsections, one section forming the thrust face extending throughout thelength of the blade and forming the main support for the forces actingon the blade, said section having a blade portion of general airfoilshape and provided with continuous outstanding ribs along the marginaledges of the side of the blade opposite that forming the thrust face,said ribs having progressively decreasing cross-sectional area from theshank to the tip end of the blade delimiting a longitudinal cavity, saidblade having a distribution of metal such that the total cross-sectionalareas thereof progressively decrease outwardly of the blade to the outerend thereof without abrupt change of section, said ribs and said cavityterminating short of the end of the blade leaving a tip portion, andanother plate-like section free of ribs and relatively thin withreference to said main thrust section extending from said shank portionand overlying said ribs and said cavity, said other section alsoextending beyond said ribs and said camber surface of said blade.

WERNER J. BIANCHARD. 76

CERTIFICATE OF CORRECTION. Petent Ne. 2,205,132 June 18, l9h0. I

t WERNER J. BIANCHARD.

It 15; hereby-certified that 'ef i'og appears in the trinteispecificatidn v of the above numbered patent reqliirifigcorreetionasfollowse Page 2, first column, line 75, for partiqn read-portionpage 5, first column, line- 56, for the word' "portions" read-poI 'tionpage 14., aecend eolumn, line 10, claim}, for 'fchamber" rpademberand thatn mia Letters P'at ant ehould be read with this borrectiontherein that the same may'eonfom te the record" of the case in thePatent Office.

Signed and sealed this 50th day or July, A. 1). 191m.

Henry Van Afadale (seal) Acting Commissioner of'Petenta.

